Hollow resonator discharge device



May 3, 1949. A. F. PEARCE 2,469,240

HOLLOW RESONATOR DISCHARGE DEVICE Filed Sept. 25, 1945 a 4 6 f z I, 9 I f E 9 l7 3, 6

-31 f 1 f 1 4 20 r 1 l8 5 w 7* z 1 I 5 J z 9 I I r a I W I CD a I l I l I l I l I INVENT0R ALBERT FREDERICK PEARCE A TTORNE Y Patented May 3, 1949 UNITED STATES PATENT OFFICE HOLLOW RESONATOR DISCHARGE DEVICE Britain Application September 25, 1945, Serial No. 618,548 In Great Britain October 18, 1941 Section 1, Public Law 690, August 8, 1946 Patent expires October 18, 1961 4 Claims.

This invention relates to electron discharge devices employing hollow resonators.

Various constructions of such devices have heretofore been proposed in which an electron beam is caused to pass through apertures in the walls of a toroidal-shaped body forming the hollow resonator. The electron beam on passing through the resonator becomes velocity-modulated and the velocity-modulated beam may then be reflected back through the apertures in the resonator so that the device can serve as a generator of self-maintained oscillations. Alternatively, the velocity-modulated beam may be caused to pass through apertures in a further hollow resonator, these two resonators being suitably coupled for the generation of self-maintained oscillation. Other constructions of discharge devices employing hollow resonators are known, the devices being suitable for use as detectors, amplifiers and mixers of oscillations of ultra-high frequency.

In general, the hollow resonators require to be tuned to the operating frequency and for this purpose the dimensions of the hollow resonator are so chosen that it resonates at a desired frequency, slight adjustment of this frequency being, however, possible by de-forming the resonator. It will be appreciated that it is necessary for that part of the resonator through which the electron beam passes to be disposed within an evacuated dielectric envelope and consequently constructional difiiculties are entailed where it is desired to eiTect adjustment of the resonant frequency by de-forming the resonator.

The object of the present invention is to provide an improved construction of electron discharge device employing one or more hollow resonators which will permit of ready adjustment of the resonator for tuning purposes.

According to the invention an electron discharge device employing a hollow resonator is provided having apertures through which an electron discharge can pass, said apertures being located within an envelope and lying between the center of the resonator and its periphery, said envelope having a re-entrant portion across which the central part of the resonator extends, whereby said control part is external to the envelope. Where it is desired to tune the resonator the tuning means are arranged to extend into the re-entrant portion and to co-operate with that part of the resonator which extends across the re-entrant portion. With such an arrangement the mechanical construction necessary for the deformation of the resonator is considerably simplified as will hereinafter be apparent. Preferably, the apertures in the resonator are of annular form and the electron beam in cross section is also preferably of annular shape which has the advantage of permitting the voltage applied to the resonator to be reduced owing to the consequent large emitting area of the cathode.

In order that the said invention may be clearly understood and readily carried into effect, it will now be more fully described with reference to the accompanying drawing which illustrates in longitudinal section one embodiment of an electron discharge device constructed according to the invention. As shown, the reference numeral I indicates an evacuated dielectric envelope having are-entrant portion 2 through the Wall of which portion the hollow resonator indicated generally at 3 is sealed. The hollow resonator is generally of toroidal form having the section shown and the aperture through which the electron beam passes is of annular form as indicated at 4. Electrons from an annular cathode 5 are caused to pass through the annular aperture 4 and are directed towards a ring-shaped reflecting electrode 6 which is maintained at a suitable potential to cause the electron beam to be reflected back through the annular aperture. The device shown in the drawing is intended to be employed as a generator of self-maintained oscillations and is suitable for use as a low powered local oscillator for a superheterodyne receiver, the oscillator operating in the region of 10,000 megacycles. The invention is of course not limited to any particular frequency. Any suitable construction of electron focussing system may be employed for focussing the electrons emitted from the cathode 5 and in the example shown a pair of ring-shaped electrodes l are employed for focussing purposes. The cathode 5 and the electrodes 7 may be supported in any suitable manner from a stem 8 which carries the usual exhaust tube 0. The reflecting electrode 6 may be supported in any suitable manner and in the example shown it is carried by rods l0 sealed to the periphery of an annular collar ll connected to the re-entrant portion 2.

It will be seen that the annular aperture 4 lies' between the center of the resonator and the periphery and that the central part of the resonator extends across the re-entrant portion 2 and hence such portion is disposed external to the envelope. Consequently, this portion of the resonator can be readily de-formed for tuning purposes and the mechanical construction necessary for such deformation can be of a relatively simple character As shown, the tuning mechanism comprises 3 a rotatable shaft l2 having a suitable knob l3 the shaft being constrained against axial movement and being rotatably mounted in. a support M which issecuredto theenvelopet The lower. end of the shaft I2 is provided with a screw-threaded portion [5 which engages a screw-threaded sleeve l6 which is secured to the part I? of the wall of the resonator which extends;acrossathefzrel-. f.

entrant portion 2, the part I] of. theresonator. being corrugated, as shown;,so':astofpermitrsaidi; part to move towards or away;-fromlthe'opposite. Wall of the resonator during tuning. Thus, when the shaft I2 is rotated the sleeve i6 is moved axially and hence moved towards or" awaylfroml the opposite wall of the resonator: This-opposite" wall is provided with a re-entrant portions-laser that tuning is effected by adjustinggthe; effective:

capacity between this re-entrant portion and? the sleeve I 6. Other ways of tuning thereson-ator can of course be employed. Further means may besprovidedzforrenabling. a. courseiandzfine adjustment of. theeresonator: to: be'. obtained; The-reentrantvportionxa may; also serve to accommodate at concentric: line 11!? which; terminates: in; a coupling; loop. ZGIDEQiGCtiTIgIiHtOTthat; portion. oii the resonator*exten'dingiacross :theizrez-entrant portion Z andwhich serlvesasithe outputkfor; theagerrerated oscillations...

,Itswill beseentifrfom thevdrawings thatzpartiof that: portion; of: the dielectric: envelope. forming: th'eire entrantvportion; 211ies-ilot-ztvl'een. the walls of therresonatorsand preferably. thistportiomof the envelope is: arranged: tollie at".a:-position:wherera voltage'sno'de. iszs'etiuprinzaccordance-.withzthe in-.

ventionzdesoribediinthe specification of Britishi Bat'enti 574,708...

The. outerportiont of; the: hollow; resonator: indicatedtbyythe: reference numeral 2;! ;-may;b'easupported: in any suitable:manner-iimrelation tbithG millimetres such a. cathode: being capable; of

emitting a: current: of. over 209; milliamperes. With such: a. largeecurrent'. flow it: is; possible: to

operate: the device: wit'hz apotential; of. the; order of250 voltsgappliedto.the'hollow'rescnatorv/hich is low; compared" with; the: potentials: necessaryin deviczesrwhere'thezcurrent flowis considerably less" than. that; referred. to alcoves. With suohza large current flow the: width of the gap" canijbegsmall thus: enabling? greater: eiiciencyrtoi' be obtained; Furthermore, owingitoiath'ezalargeicathodeiemissive areamhich; is a'vailable; it islpossiblezthat the. de-' vice findrapplicationlfor-the: generation of oscillations of. high: peak: power: by applying: to the:. hollow: resonator: pulses of high. voltage; and

short: .durati'orn- If: the: device is so: used; peak powers: of? the order of] kilowatts I may he obtainabler Although: the invention: has: been. described above:aszapplied:toamoscillatorintwhichianvelocity modula-tediheamtis reflectedsbackthroughzthe resonator; it: Willi bezunderstoodrthatz the inven- 4 tion is equally applicable to electron discharge devices employing one or more hollow resonators when. designed for use. for. other. purposes.

In particul'an'the device-shown inzthe; drawing may be employed for mixing high-frequency oscillations, in which case the intermediate frequency output may be taken from the electrode 6: whiclirinthis; example, may serve as a target electrode for. the. higher velocity electrons in ,linowni manner; Further, the invention is not limited. to. devices employing velocity-modulation", since the invention may be applied to devices in which a hollow resonator forms the inputi'circuit ofa conventional form of thermionic valve if desired, the re-entrant portion 2 may be extendediso' as to provide a support for the annular cathode 5 and the focussing electrode 1. The cathode and focussing electrodes may be mounted on rings of .insulating material so as torfornn ai unitary structureanddthetinnerreiiges tuned. by; -tuning:rmechanismss disposed; at 'opof said ringsimay, engage-i a pluralityiofzprotrusions zformed in: the portions 2:.an-di extendingdnto the evacuated. space whereby the structure can 1 be alignediwith r.espect'.jto.=the apertures similar taithe:arrangementzdescribed inithexspecification of British "Patent: No. 50.7;85l'0. 'l'iikewise, the l fl rode ii mav'bea mounted :on .ringsrcf-insulating -material: and aligned-by; the: provision? of protrusions: formed in; the: portion 2;. :In: some .casesthere-entrant. portion may extendlal'ong the: whole length: oi-- theenvelope lr, so-that. the envelopa; together? with the reeentrant portion, provides an evacuated space: of; annular. cross- ,section along; its:- lengths SllCha a. constructiqn employe'dvsin'oe .itz p'errnitsboth: resonators: toabe posite.ends-oftheenvelope.

For-f highi powered: devices cooling arrangements may be necessary. For example, timer-hollow. resonator-or. resonatorsmayrbe ,providediwith cooling fins. ;liu.rther;-,in:thezconstructionashown in? the: drawing; water; coolingaofi the: reeentrant portion: .2imay, -.be; employed. Whererthememn- 'tranttportion'; extends alongsthe: iwholenlengthi of the; envelope; airi or: watermay 1e: forcedxalong theirs-entrant; portion entering; at:- oneeirdzand beingexhaustediatizthez.other; end';.suitable apertures-being: prcm'ded: in: thesp'ortioni of; the: resonator: or resonators: extendingcacross the reentrant. portion to 1 permit: of: a through: flbwoft air or'waterr.

What I claim is: l Anlelectron' dischargegdeyiceihamngsanievacdated; envelope provided-1 withz a tubular reentrant porticn,. a c'avityfresonatortsealed through and: means? for collecting: sa-idi -electrorn-stream,

sai'dzlasttwo mean'sabeing within. saidlevacuated pantni saidlenvelop'e'; aiportionzofthe wallicftsaid cavity resonatcriportionrexternal ofrsaidlevacuing said: flexible: wall; portionv for tuning said resonator:

An; electron discharge: device-1 having: an

.evacuatedrenvelope provided; with; a; tubular reentrant portiom. a cavity resonator extending rial-1s.versely: either-tubular reentrant; portion. or

said envelope with a portion of said resonator external of said envelope and a portion within said envelope, the walls of said resonator being sealed through the Walls of the tubular portion of said envelope, said resonator being provided with an apertured portion adjacent its periphery and within said evacuated envelope, an annular cathode means Within said envelope registering with the apertured portion of said resonator for directing electrons through said apertured portion, an annular collector associated with said resonator for receiving said electrons, one Wall of the resonator within the reentrant portion of said envelope and outside the evacuated portion of the envelope being corrugated for rendering said wall flexible, and means for flexing said resonator wall for tuning said resonator.

3. An electron discharge device having an envelope provided with a tubular reentrant portion, a cavity resonator extending transversely of the tubular reentrant portion of said envelope with a portion of said resonator external of said envelope and a portion within said envelope, the walls of said resonator being sealed through the walls of the tubular portion of said envelope, said resonator being provided with an apertured portion adjacent its periphery and within said evacuated envelope, an annular cathode means registering with the apertured portion of said resonator for directing electrons through said apertured portion and annular collector for receiving said electrons, one wall of the resonator within the reentrant portion of said envelope being corrugated for rendering wall flexibl and means for flexing said Wall for tuning said resonator, said last means comprising a threaded element supported by said flexible wall and screw element rotatably supported at the open end of said tubular portion for causing movement of said threaded element for flexing the wall of said resonator for tuning said resonator.

4. An electron discharge device having an evacuated envelope provided with a tubular reentrant portion, a cavity resonator extending transversely of the tubular reentrant portion of said envelope with a portion of said resonator external of said envelope and a portion within said envelope, the walls of said resonator being sealed through the walls of the tubular portion of said envelope, said resonator being provided with an 'apertured portion adjacent its periphery and within said evacuated envelope, an annular cathode means within said envelope registering with the apertured portion of said resonator for directing electrons through said apertured portion, an annular collector associated with said resonator for receiving said electrons, one wall of the resonator within the rentrant portion of said envelope and outside the evacuated portion of the envelope being flexible, and means for flexing said resonator wall for tuning said resonator.

ALBERT FREDERICK PEARCE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,167,201 Dallenbach July 25, 1939 2,242,275 Varian May 20, 1941 2,259,690 Hansen et al. Oct. 21, 1941 2,343,487 Strudel Mar. '7, 1944 

